Peculiarities of the genre
As for the peculiar features of philosophic novel first of all it is important to say that the main feature is a presence of author in the novel. As a matter of fact, the philosophic novel is an implementation of a soul of author. So, it is common that among words characters say there are words of the author. Characters are means to express the ideas of author.
It is also common for philosophic novel to develop not around actions but around feelings, foundations of people and their thoughts. It is common for novels to be full of dialogues that deal with some secrets and actions of other people. Though, when talking about philosophic novel dialogues deal with philosophic thoughts of characters.
Those are ideas of characters about life, about people, about do's and don'ts and about a number of other psychological and philosophic stuff. Another peculiar feature of philosophic novel is the end of the novel. Those always end with happy-ends though those are not common happy ends. It is not that everyone is happy and in-love.
It is when the main character finds the mental peace and the answer for the main question that disturbed his mind. Say, "Crime and Punishment" philosophic novel. The main character is imprisoned in the end, though it is a happy end. Raskolnikov is in material prison though he is released of the prison of his mental sufferings.